a) Field of the Invention
The present invention relates a compact vari-focal optical system, and more specifically to a compact vari-focal optical system which is to be used in a digital camera, a portable terminal, a portable telephone and the like.
b) Description of the Prior Art
Vari-focal optical systems for compact cameras, portable terminals, portable telephones and the like which use electronic image pickup devices such as a CCD strongly require compactness or thin compositions in particular. Known as a conventional example of such a compact vari-focal optical system is an optical system which is disclosed by the following literature.
[Patent literature No. 1] Japanese Patent Kokai Publication No. Hei 10-333034